Getter shield pickup loop



1957 H. J. DAILEY ET AL 2,813,216

GETTER SHIELD PZCKUP LOOP Filed April 21, 1953 6 Fig.2.

- INVENTORS HAMPTON J. DAILEY, DECEASED,

BY RUTH M. DAILY, EXECUTRIX AND 5 HAROLD RAPAPORT WITNESSES:

ATTORNEY United States Patent GETTER SHIELD PICKUP LOOP Hampton J. Dailey, deceased, late of Verona, N. 1., by Ruth M. Dailey, executrix, Verona, N. J., and Harold Rapaport, New York, N. Y., assiguors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 21, 1953, Serial No. 350,092

7 Claims. (Cl. 313-174) Our invention relates to electron tube construction, and

more particularly to a cathode shield for an electron tube.

In accordance with the prior art of which we are aware, getters have been provided in vacuum tubes for cleaning up residual gas in vacuum tubes by chemical combination and adsorption after the tubes have been pumped out and sealed. The getters are usually vaporized by placing them, while inside of the vacuum tube, in a high-frequency field. The getter elements are thus heated, and some of the getter material is caused to be evaporated. The vaporized metal deposits on the wall 'of the tube and collects the gas molecules by chemical combination therewith. These pieces of getter material are usually placed in the tube in a position where they are substantially isolated from the remaining elements of the tube, particular care being exercised to prevent the deposition of the getter material on the insulators in the region of the high potential electrodes. A cathode shield is therefore frequently provided to shield the envelope of the tube, in the region of the electrodes from contamination by the getter material.

Heating the getter material, with a high frequency field, to the point of vaporization, requires a very large amount of power and great care is required to prevent overheating other elements of the tube.

It is accordingly an object of our invention to provide a vacuum tube structure including a getter element Whereby a relatively weak radio frequency field is suflicient to flash the getter.

It is another object of our invention to provide a structure combining the features of a cathode shield and a getter pickup loop.

It is an ancillary object of our invention to provide an improved getter mounting structure.

It is still another ancillary object of our invention to provide a new and useful electronic apparatus.

The invention with respect to both the organization and the operation thereof, together with other objects and advantages may be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Figure 1 is a plan view of a getter shieldbuilt in accordance with our invention, and

Fig. 2 is an elevational view partly in cross section of a portion of the vacuum tube structure shown in Fig. 1, taken along the line IIII of Fig. 1.

In accordance with our invention we provide a vacuum tube envelope 4 having extending through the wall thereof a first cathode lead 6 and a second cathode lead 8. The walls 4 of the envelope are preferably of a dielectric material such as glass so that it provides an insulation between the cathode leads 6, 8. A cathode 10 is provided inside the envelope having one end connected to the first lead 6 and the other end connected to the second lead 8. Surrounding the cathode leads 6, 8 a short distance from their junction with the envelope 4, is a cathode shield 12 which serves to protect the region of the tube where the high potential electrodes are located from contamina- 2,813,216 Patented Nov. 12, 1957 tion by the getter material. The cathode shield 12 comprises a flat piece of metal encircling the two cathode leads and substantially filling that end of the envelope. At the edge of the cathode shield 12 there is a flange 14 which bends downward toward the region where the cathode leads join the tube envelope. The flange 14 employed in the preferred embodiment of our invention serves to aid in confining the getter material to the lower part of the tube. In the region of the first cathode lead 6, the cathode shield 12 has a flange 16 which is adapted to engage the first cathode lead 6 so as to provide support for the shield 12. In the region of the second cathode lead 8 the shield 12 is cut away sutficiently to prevent electrical connection between the second cathode lead 8 and the shield 12.

A slot 18 is cut across the shield which in the preferred embodiment of our ihvention extends approximately threequarters of the distance across the shield 12. However, in accordance with the broader aspects of our invention the slot may extend a much shorter distance and in some instances it is believed that a slot extending one quarter of the way across the shield would be suflicient. The slot 18 preferably extends in a direction perpendicular to an axis through the two cathode leads 6, 8. However, in accordance with other embodiments of our invention the slot could cut through the shield at other places such as through the thin strip 19 opposite an electrode lead hole. Near the end of the slot 18 at the edge 14 of the disc 12 there is provided a getter wire 20. The getter wire 20 may be composed of any of a large number of materials which are well-known in the art such as barium or magnesium which are easily vaporized and which produce a getter effect. The getter wire 20 is connected to the under side of the shield 12 near an edge of the shield at one side of the slot 18, extends across the slot 18 and is connected to the under side of the shield 12 near the edge thereof at the other side of the slot 18.

A cathode shield 12 is thus provided which when placed in a high-frequency field acts as an antenna or pickup loop since the only connection between the two halves of the shield 12 at one end of the shield is the getter wire 20. The shield tends to concentrate the electromagnetic oscillations, which it has absorbed, in the getter wire. Thus, high-frequency electromagnetic fields of relatively low power in the region of the vacuum tube can produce substantial heating in the getter 20 without producing excessive heating of the other elements of the tube.

Although we have shown and described specific embodiments of our invention, we are aware that other modifications thereof are possible.

We claim as our invention:

1. An electron tube comprising a vacuum-tight envelope, a cathode element inside said envelope, said element having two leads for applying current thereto, said leads extending through said envelope, a getter shield surrounding said leads and supported by one of said leads, said getter shield comprising a circular piece of metal having a slot cut at least half way across said shield, a strip of getter material anchored at each end thereof to said shield and extending across said slot near the edge of said shield.

2. An electron tube comprising a vacuum-tight envelope, a cathode element inside of said envelope, said cathode element having two leads extending through said envelope for supplying current to said element, a getter shield comprising a substantially flat piece of metal lying in the region around said leads inside of said envelope and making physical contact with one of said leads, the outer edges of said getter shield being flanged at an angle to the main body of said getter shield, said shield having a slot therein extending into said getter shield at least one fourth of the distance across said shield, a strip of getter material extending across said slot near the edge of said disc and being anchored at each end to said disc.

3. An electron tube comprising a vacuum-tight envelope having therein a cathode element having leads connected thereto extending through said envelope, a cathode shield surrounding said leads and lying substantially perpendicular to said leads, said cathode shield comprising a substantially flat piece of metal having flanges which are bent in the opposite direction from said cathode heater, 2. flange on said disc adapted to contact one of said cathode leads, said shield making physical contact with said lastmentioned lead through said last-mentioned contact flange, a slot extending from an edge of said shield a substantial distance intosaid shield, a strip of getter material attached to said shield on one side of said slot near an edge of said shield extending across said slot and making contact with said shield on the other side of said slot near the edge of said shield.

4. An electron tube comprising a vacuum-tight envelope, a cathode element inside said envelope, said element having two leads for applying current thereto, said leads extending through said envelope, a getter shield surrounding said leads and supported thereby, said getter shield comprising a generally circular disc of metal having a slot cut at least one quarter of the distance across it, a strip of getter material anchored at each end to said shield and extending across said slot near the edge of said shield.

5. An electron tube comprising a vacuum-tight envelope, an electrode lead extending through said envelope, a getter shield comprising a substantially flat piece of metal lying in the region around said lead inside of said envelope and supported by said lead, said getter shield having a slot extending into said getter shield at least one quarter of the distance across said shield, a strip of getter material extending across said slot near the edge of said disc and being anchored at each end to said disc.

6. An electron tube having therein a getter shield, said getter shield comprising a substantially flat piece of metal having flanges at the edges thereof, said getter shield having a slot extending from an edge of said shield a substantial distance across said shield, a strip of getter material attached to said shield on one side of said slot near an edge of said shield and extending across said slot and making contact with said shield on the other side of said slot near the edge of said shield.

7. An electron tube comprising a vacuum-tight envelope, a getter shield in the form of a thin sheet of material inside said envelope, said shield having a discontinuity therein extending inward from an edge thereof, a strip of getter material extending across said discontinuity and being connected to said shield near an edge thereof on each side of said discontinuity.

References Cited in the file of this patent UNITED STATES PATENTS 

